Icemaker refrigerator provided therewith and ice making method

ABSTRACT

An icemaker for a refrigerator is provided that includes a mold container which may be filled with water, an air space adjacent to a water level in the mold container, and an air humidifying device for increasing the level of humidity in the air above the water level. Water is administered to the mold container and is cooled and ice crystals form when a given crystallization temperature of the water of below zero degrees C is reached.

The present invention relates to an ice-maker comprising a mold container which can be filled with water and which, for ice-making, can be cooled to a temperature below 0° C., a refrigeration appliance provided therewith and an ice-making method which can be carried out, in particular, with an ice-maker of this type.

Most conventional ice-makers make use of a mold container in which a plurality of compartments which, when filled, communicate with one another, is provided. Examples of ice-makers of this type are described in DE 4 113 767 C2 and DE 2 429 392 A.

There are two important reasons for providing a connection between the compartments of the mold container. Firstly, the connection facilitates automatic filling of the mold container, since water can be fed into the mold container at a single site and can spread out from there into the mutually communicating compartments. A further reason is the mechanism of ice formation. Ice formation starts, according to a process known as heterogeneous nucleation, not at 0° C, but at a few degrees below 0° C. It relies on the presence of heterogeneous, that is non-aqueous nucleation seeds and if these are lacking, water can be cooled to −40° C. without freezing. This effect in an automatically operating ice-maker is undesirable for a variety of reasons. Firstly, if the compartments do not communicate, there is a risk that nucleation seeds are lacking in individual compartments, so that the water therein remains liquid, while in other compartments it has long since frozen. If the content of the compartments is emptied into an ice storage container and a compartment still contains water, the water freezes in the storage container, so that the finished pieces of ice therein freeze together into a block that is no longer easily handled. In order to reduce the probability of this, either a long waiting time must be allowed for before the emptying of the compartments, in order to give compartments without efficient nucleation seeds the opportunity to freeze, which severely reduces the productivity of the ice-maker, or the ice-maker must be operated at extremely low temperatures, which can only be maintained with a large energy input. Conventionally, these problems are circumvented by allowing the compartments of the mold container to communicate with one another during freezing, so that ice formation from one compartment in which an effective nucleation seed enables early freezing spreads into all the other compartments. In this way, however, only mutually connected ice pieces can be obtained and these do not break apart reliably on removal from the mold and therefore take up a large amount of space in a collecting container and are difficult to handle.

The object of the present invention is to provide an ice-maker, a refrigeration appliance provided therewith and an ice-making method which function rapidly and efficiently with a small input of energy.

This aim is achieved, firstly with an ice-maker comprising a mold container which can be filled with water and an air space adjacent to a water surface in the mold container, wherein an air humidifier is provided to enrich the air over the water surface with moisture. By this moisture condensing out in the form of tiny snow flakes, highly efficient nucleation seeds are obtained which precipitate on the water surface and from there are able to initiate the ice formation at temperatures only slightly below 0° C.

In the simplest case, the air humidifier is an evaporator.

In order to enable rapid and efficient warming of the water in the evaporator, a water container of the evaporator preferably has a wall which is at least partially made from an electrically conductive plastic which, for heating thereof, has a current applied thereto.

In order to prevent deposition of limescale in the evaporator, said evaporator is preferably configured to heat the water contained therein to a maximum of 60° C.

The evaporator has a water capacity of preferably not more than 2 cm³ in order firstly to enable rapid heating of the water contained therein, and secondly to keep low the quantity of heat emitted to the water in the evaporator and subsequently via said evaporator to the whole ice-maker.

A control device is preferably provided for the temporary operation of the air humidifier during each ice-making process.

The control device can be coupled to a timer in order to operate the air humidifier with a pre-determined delay in each case after filling of the mold container. Alternatively or in addition thereto, said control device can also be coupled to a temperature sensor in order to operate the air humidifier once a pre-determined temperature in the air space has been fallen below.

The mold container and the air humidifier are suitably connected to a common water supply line.

The air humidifier can be configured to deliver water to the mold container once a target fill level is exceeded. This renders unnecessary precise dosing of the water quantity fed into the air humidifier.

It is expedient, in particular, if the air humidifier is arranged in the water supply line upstream of the mold container.

Since a large number of nucleation seeds is generated with the snow crystals, the mold container can have a plurality of ice compartments that are not mutually connected, without a high risk of the water not freezing in individual compartments. Unconnected ice pieces are obtained from the unconnected compartments and these ice pieces can be handled easily and reliably.

A blower for driving air circulation in the air space is expediently provided, in order to achieve distribution of the snow crystals over the whole of the water surface.

The ice-maker can be provided with a dedicated refrigeration appliance. The ice-maker is preferably built into a refrigeration appliance in order to be cooled by the refrigeration unit thereof.

The above mentioned blower can also be part of the refrigeration appliance and, in particular, can serve to drive air circulation between the air space and a refrigerant evaporator.

Air circulation of this type serves at the same time to cool the water in the mold container or contributes at least substantially to the cooling thereof. In order to prevent the water in the air humidifier freezing earlier than that in the mold container, the air circulation over the water surface of the air humidifier is preferably weaker than that over the water surface of the mold container.

The object of the invention is further achieved by a method for producing ice pieces, in particular in an ice-maker or a refrigeration appliance, as defined above, comprising the following steps:

-   -   dosing water into a mold container,     -   cooling the water,     -   applying ice crystals to the water when a pre-determined         inoculation temperature of the water below 0° C. is reached.

The ice crystals are preferably obtained by evaporation of water and cooling the vapor thereby obtained to below 0° C. Inoculation of the water with the ice crystals preferably takes place at a water temperature of between −2° C. and −7° C., wherein in the case of ice making in a thermostatically controlled cooling chamber of a refrigeration appliance, the inoculation temperature can be selected to be higher the lower the target temperature of the thermostat regulation is. The air temperature in the ice-maker is generally lower at the time of the inoculation and a temperature of −10° C. is preferable.

Further features and advantages of the invention are disclosed by the following description of exemplary embodiments, making reference to the drawings, in which:

FIG. 1 shows a schematic section through a refrigeration appliance with an ice-maker according to the present invention,

FIG. 2 shows a perspective view of an exemplary embodiment of the ice-maker according to the invention, and

FIG. 3 shows a graphical representation of the change in temperature and air humidity over time during an ice-making cycle.

The refrigeration appliance shown in schematic section in FIG. 1 has a heat-insulating body 1 and a door 2, which delimit an interior space 3. The interior space 3 is kept by an evaporator, which is accommodated in the evaporator chamber 4 in the upper region of the body 1, at a temperature of below 0° C. An automatic ice-maker 5, which is described below in greater detail by reference to FIG. 2, is arranged in the immediate vicinity of the evaporator chamber 4 in the interior space 3, so that cold air can be efficiently applied to said ice-maker 5 from the evaporator chamber 4.

Arranged under the ice-maker 5 is a collecting container 6 of an ice dispenser, said collecting container 6 receiving ice pieces ejected by the ice-maker 5. The collecting container 6 extends over a large part of the depth of the interior space 3. Accommodated in a rearward recess 7 of the collecting container 6 is an electric motor for driving a stirring paddle 8 which extends in the longitudinal direction of the collecting container 6. One end of the stirring paddle 8 facing away from the recess 7 extends into a cylindrical dispensing chamber 10. Knives 9 of a grinding device are fastened to a sleeve surrounding the end of the stirring paddle 8 and can be coupled via a clutch 11 to the rotation of the stirring paddle 8. A second group of knives 12 can be fixed to the cylindrical outer wall of the dispensing chamber 10, so that the knives 9, when they are carried along by the rotation of the stirring paddle 8, each leave intermediate spaces between the knives 12 and thus chop the ice pieces conveyed out of the collecting chamber 8 into the dispensing chamber 10 before said ice pieces fall out of the dispensing opening 13 into the lower region of the dispensing chamber 10. The locking of the knives 12 to the wall of the dispensing chamber 10 is releasable, so that the knives 12 are carried along by the rotation of the knives 9, with the result that the intact ice pieces are dispensed from the dispensing opening 13. When the clutch 11 is open, neither the knives 9 nor the knives 12 are carried along by the rotation of the stirring paddle 8. In that the stirring paddle 8 is automatically rotated from time to time with the clutch 11 open, it is possible to prevent freezing together of ice pieces in the collecting container 6 and to keep them movable so that, when required, they can be reliably dispensed through the dispensing opening 13.

The dispensing opening 13 lies opposed to a channel 14, which extends through an insulating material layer of the door 2 and opens into a recess 15 which is open toward the outside of the door 2. A flap 16 holds the channel 14 closed for as long as the dispenser is not in operation, which means that the stirring paddle 8 rotates with the clutch 11 closed, in order to dispense ice through the dispensing opening 13 and the channel 14 into a container placed in the recess 15.

A water tank 17 is embedded in the rear wall of the recess 14 in the insulating material of the door 2. The water tank 17 is connected, on one side, like the ice-maker 5, via a supply line 18 and a shut-off valve 19 to the drinking water mains and, on the other side, to a supply point 20 in the recess 15.

A detailed description of the ice-maker 5 follows, making reference to FIG. 2. The figure shows an injection-molded rectangular frame 21 made from plastics, in which a mold container 22 with, in this case, seven compartments 23 is suspended pivotable about a longitudinal axis 24. A motor and a gearbox for driving a pivot movement of the mold container 22 about the longitudinal axis 24 are, respectively, accommodated in two hollow wall parts 25, 26 of the frame 21. In the orientation shown, separating walls 27 are arranged between the compartments 23 of the mold container, abutting one side.

Fastened above the mold container 22 on the wall part 26 is a small flat tray 28. A hollow web 29, which can be equipped with an electrical heating rod 30 from the side of the wall part 26, is provided on the base of the tray. Alternatively, the tray 28 itself or a part thereof can also be formed from a plastic which is made electrically conductive with a suitable additive material, such that said tray can be heated by passing a current through it. The supply line 18 opens into the tray 28. A plurality of broad cut-outs 31, 32 is formed in the side walls of the tray 28. Pillars 33 are left between the cut-outs 31, 32 in order to carry a cover 34. Formed at the deepest cut-out, identified as 32, is an overflow lip 35 via which the water can flow out of the tray 28 into the mold container 22. The capacity of the tray 28 is substantially less than that of the mold container 22, at only a few cm³, more particularly less than 1 cm³.

At the start of the ice making cycle, the shut-off valve 19 which supplies the ice-maker 5 is temporarily opened in order to let water in. The water flows into the tray 28 and passes via the overflow lip 35 into the mold container 22. The quantity of water fed in is dosed so that it just suffices to flow over the separating walls 27 at their lower-lying end. This ensures even filling of all the compartments 23 of the mold container 22. The mold container 22 is then slightly rotated clockwise about the axis 24 until the upper edges of the separating walls 27 are horizontal and lie higher than the water surface in the compartments 23, so that the water portions in the compartments 23 are separated from one another.

In this position, the water in the compartments 23 is cooled. A temperature sensor (not shown) is provided in order to monitor the temperature of the water and to communicate it to a control circuit (not shown). The temperature sensor can be placed directly at the mold container in order to detect the actual temperature of the water in the compartments 23. It is also conceivable to place said sensor at another site, for example, at the frame 21, so that it detects the temperature of the air in the ice-maker, although then the control circuit is designed to estimate the water temperature based on the measured air temperature and the cooling time. The control circuit can be a central control circuit of the refrigeration appliance which is also responsible for the temperature regulation of the interior space 3, or it may be a dedicated control circuit of the ice-maker 5.

While the water in the compartments 23 cools, the heating rod 30 can be operated at a low power level sufficient to prevent freezing of the water in the tray 28. If the water temperature in the compartments 23 detected by the sensor or estimated by the control circuit drops below a pre-determined limit value, the control circuit switches the power of the heating rod 30 to high in order to heat the water in the tray 28. The limit value is typically selected to lie within the temperature interval from −6° C. to −3° C. Particularly if the same control circuit is responsible for the control of the ice-maker 5 and for the temperature regulation of the interior space 3, the limit value can expediently be pre-determined as a function of the target temperature of the internal space 3.

Due to the heating, some of the water in the tray 28 evaporates and water vapor passes out through the cut-outs 31, 32. The power of the heating rod 30 is controlled such that the water in the tray 28 is not heated above 60° C., in order to prevent limescale forming on the walls of the tray 28. This water vapor forms a fine mist of snow or ice crystals, which is distributed over the mold container 22 by the draught prevailing due to the air exchange with the evaporator chamber 4. Thus crystals which serve as nucleation seeds are reliably distributed to each compartment 23 and initiate the ice formation there.

Due to the ice formation, heat is released. The above mentioned dependency of the temperature limit value on the target temperature of the interior space 3 is suitable for preventing this heat from leading to re-thawing of the previously formed ice in the compartments 23. Given a low target temperature and a correspondingly low temperature of the air fed out of the evaporator chamber 4, the heat released during ice formation can be rapidly conducted away, so that the temperature in the compartments 23 also does not reach 0° C. again when the inoculation with snow crystals has already been carried out at a relatively high water temperature in the compartments 23 of −3° C. In the case of a relatively high target temperature of the interior space of, for example, −14° C., the heat released on ice formation cannot be conducted away so rapidly, so that it is suitable to carry out the inoculation at a lower water temperature in the compartments 23 of approximately −6° C.

Since it can be assumed with certainty that, following inoculation with the snow crystals, ice formation has taken place in each individual compartment 23, the time between the inoculation and a subsequent emptying of the compartments 23 can be made relatively short, so that the compartments are soon available again for refilling.

In order to facilitate emptying, the mold container 22 is provided at a base side (not shown in FIG. 2) with an electrical heater. Once, following inoculation, a time period sufficient for complete freezing has elapsed, the control circuit activates the heater in order to melt the ice pieces in the compartments 23 at their surface and then activates the motor in order to rotate the mold container 22 about the longitudinal axis 24, inverting it so that the ice pieces fall out of the compartments 23 into the collecting container 26 placed beneath.

As the mold container 22 is rotated in the same direction, the position shown in FIG. 2 is reached again and a new ice making cycle can begin again with the filling of the compartments 23.

FIG. 3 shows, by way of example, the variation of the water temperature in the compartments 23, the water temperature in the tray 28 and the air humidity in the ice-maker during an ice making cycle. The temperature in the compartments 23 is represented by the continuous line 36 and the associated temperature scale is shown on the left side of the graph, while the percentage air humidity is shown as a dashed line 37 and the temperature of the tray 28 is shown as a dot-dashed line 38, a scale for both (in percent and degrees Celsius) is shown at the right side of the graph. The working cycle begins at approximately 18:30 with the filling of the mold container 22. The temperature of said mold container 22 is approximately 9° C. at this point in time, since it has previously been heated in order to eject the ice pieces from the preceding cycle. The tray 28 is warmed to approximately 0° C. by the feeding in of fresh water. The air humidity is at a temporary maximum due to the heating of the mold container 22.

During the following 12 minutes, the mold container 22 cools significantly faster than the tray 28 and reaches a temperature of −4° C. The more rapid cooling of the mold container 22 is mainly a consequence of the air fed into the ice-maker 5. By means of suitable placement of air channels, deflector plates or the like in the ice-maker 5, it is ensured that the overwhelming majority of the cold air flowing through the ice-maker 5 flows along, and cools, the mold container 22, while the flow rate in the vicinity of the tray 28 is kept substantially less. The use of an effectively heat-conducting material, such as aluminum, and the mounting of cooling ribs on the underside (not shown in FIG. 2) of the mold container 22 also ensures rapid heat exchange, whereas the tray 28 is preferably made from a poorly heat-conducting plastic and the cover 34 placed thereover ensures that only a weak air flow passes through the cut-outs 31 and over the surface of the water in the tray 28. It can also be provided, as stated above, that the heater rod 30 of the tray 28 is also in operation during the cooling phase at a low power level that is set to be just sufficient in order to prevent freezing of the water in the tray 28.

As the limit temperature is detected at approximately 18:41, the control circuit switches the heating rod 30 to a high power, so that the tray 28 is heated to approximately 50° C. within a minute. Water vapor which forms in the protected space between the water surface of the tray 28 and the cover 34 is flushed out of the cut-outs 31, 32 and is distributed in the air space over the mold container 22. The air humidity curve 37 reaches a maximum again. The snow crystals thereby formed initiate the ice formation, leading to a marked rise in the temperature of the mold container 22 to approximately −1° C. A cooling phase lasting approximately half an hour follows until, at approximately 19:15, the heater in the mold container 22 is started and the mold container is inverted in order to eject the finished ice pieces.

Since the tray 28 is heated only very briefly, the quantity of energy required is small. Assuming 25 ice making cycles per day, a heating power of 50 Watt, and a heating duration of 70 seconds in each case, the daily energy requirement is 0.024 kWh. The productivity of the ice-maker that can be achieved with this measure with a temperature in the interior space 3 of −14° C. is higher than that of a conventional ice-maker without inoculation, which is operated at −18° C. The energy saving achievable thereby exceeds the energy expenditure for the water vapor production by many orders of magnitude. 

1-25. (canceled)
 26. An ice-maker comprising: a mold container configured to be filled with water and an air space adjacent to a surface of water in the mold container; and an air humidifier, the air humidifier being operable to humidify air in the air space above the surface of water in the mold container to thereby bring the air to a predetermined moisture level.
 27. The ice-maker as claimed in claim 26, wherein the air humidifier is an evaporator.
 28. The ice-maker as claimed in claim 27, wherein the evaporator comprises a heatable water container.
 29. The ice-maker as claimed in claim 28, wherein the heatable water container comprises a wall which is at least partially made from an electrically conductive plastic.
 30. The ice-maker as claimed in claim 26, wherein the evaporator is configured to heat water contained therein to a maximum of 60° C.
 31. The ice-maker as claimed in claim 26, wherein the evaporator comprises at least one air exit opening through which vapor generated can escape and thereafter be deflected toward the mold container.
 32. The ice-maker as claimed in claim 26, wherein the evaporator has a water capacity of not more than 2 cm³.
 33. The ice-maker as claimed in claim 26 and further comprising a control device for the temporary operation of the air humidifier during each ice making process.
 34. The ice-maker as claimed in claim 33, wherein the control device is coupled to a timer in order to operate the air humidifier with a pre-determined delay after a filling of the mold container with water.
 35. The ice-maker as claimed in claim 33, wherein the control device is coupled to a temperature sensor in order to operate the air humidifier once the temperature in the air space has dropped below a pre-determined temperature.
 36. The ice-maker as claimed in claim 26, wherein the mold container and the air humidifier are connected to the same water supply line.
 37. The ice-maker as claimed in claim 26, wherein the air humidifier is configured to deliver water to the mold container once a target fill level has been exceeded.
 38. The ice-maker as claimed in claim 36, wherein the air humidifier is arranged in the water supply line upstream of the mold container.
 39. The ice-maker as claimed in claim 26, wherein the mold container comprises a plurality of ice compartments that are not mutually connected.
 40. The ice-maker as claimed in claim 26 and further comprising a blower for driving air circulation in the air space.
 41. The ice-maker as claimed in claim 40, wherein air guides are provided which deflect the air stream delivered by the blower at least partially over the surface of water in the mold container.
 42. A refrigeration appliance comprising: a housing; and an ice-maker having a mold container configured to be filled with water and an air space adjacent to a surface of water in the mold container; and an air humidifier, the air humidifier being operable to humidify air in the air space above the surface of water in the mold container to thereby bring the air to a predetermined moisture level.
 43. The refrigeration appliance as claimed in claim 42 and further comprising a blower that drives air circulation between the air space and a refrigerant evaporator and thereby cools the air space.
 44. The refrigeration appliance as claimed in claim 43, wherein the air circulation is weaker over a water surface of the air humidifier than over the water surface of the mold container.
 45. A method for producing ice pieces, the method comprising: dosing water into a mold container; filling an evaporator; cooling the water; and applying ice crystals to the water once a pre-determined inoculation temperature of the water below 0° C. is reached.
 46. The method as claimed in claim 44, wherein the steps of dosing water into a mold container and filling an evaporator take place simultaneously and the steps of cooling the water and applying ice crystals to the water take place sequentially, beginning with the step of cooling the water.
 47. The method as claimed in claim 44, wherein the steps of dosing water into a mold container, filling an evaporator, cooling the water, and applying ice crystals to the water take place sequentially, beginning with the step of dosing water into a mold container.
 48. The method as claimed in claim 45, wherein the ice crystals are obtained by evaporation of water and cooling the vapor obtained to below 0° C.
 49. The method as claimed in claim 45, wherein the inoculation temperature lies in the range of −2° C. to −7° C.
 50. The method as claimed in claim 45, wherein the evaporation of water takes place over a time span of 0.5 minutes to 2.5 minutes.
 51. The method as claimed in claim 45, wherein the evaporation of water takes place over a time span of 1 minute to 2 minutes. 